It is well known to provide a refrigeration system including a refrigeration device such as a refrigerated case, refrigerator, freezer, etc. for use in commercial and industrial applications involving the storage and/or display of objects, products and materials. For example, it is known to provide a refrigeration system with one or more refrigerated cases for display and storage of frozen or refrigerated foods in a supermarket to maintain the foods at a suitable temperature (e.g. 32 to 35 deg F.). In such applications, such refrigeration systems often are expected to maintain the temperature of a space within the refrigerated case where the objects are contained within a particular range that is suitable for the particular objects, typically well below the room or ambient air temperature within the supermarket. Such known refrigeration systems will typically include a heat exchanger in the form of a cooling element within the refrigeration device and provide a flow of a fluid such as a coolant into the cooling element to refrigerate (i.e. remove heat from) the space within the refrigeration device. Such known refrigeration systems may also include sensors such as thermometers (or thermoswitches) and some type of control system (or timer) intended to provide for the regulation of the temperature within the refrigerated case. Various known configurations of refrigeration systems (e.g. direct expansion system and/or secondary system, etc.) are used to provide a desired temperature within a space in a refrigeration device such as a refrigerated case (e.g. by supply of coolant).
It is also well known that over time in the use of a refrigeration system, ice and/or “frost” may accumulate on the cooling surfaces of a cooling element within the refrigerated case as water vapor condenses and “freezes” on the cooling surfaces. As ice or frost form or accumulate on the cooling surfaces, the ability of the refrigeration system to provide control or regulation of the temperature within the refrigerated case may be impaired. The presence of ice or frost on the cooling surfaces typically reduces the efficiency of heat transfer from the cooling element to the air within the space of the refrigerated case. The accumulated ice or frost may act as an “insulator” on the cooling surfaces and therefore additional energy may be required to maintain the desired temperature within the refrigerated case. The amount of ice or frost that may accumulate on the cooling surfaces may be influenced by a wide variety of factors, such as the humidity level in the air (i.e. moisture), the type of objects within the refrigerated case, the design of the refrigerated case (e.g. open or enclosed by doors or the like), the nature or manner of use, the environment in which the refrigerated case is used, etc.
It is known to provide a defrost system for a refrigeration system. The general intent of such known defrost systems is to remove the accumulated ice or frost from the cooling surfaces, typically by elevating the temperature of the cooling surfaces above the ice-water freezing point (i.e. above 32 deg F.) so that any ice and frost that may have accumulated will melt. According to one known arrangement, the defrost system may simply involve temporarily turning off the refrigeration system (i.e. interrupting the flow of coolant to the cooling elements within the refrigerated case) for a designated time. This arrangement may not be able to achieve the objective of removal of the ice and frost within a suitable period of time; variations in the temperature within the refrigerated case may be unacceptable, requiring that the objects be removed from the refrigerated case. According to another known arrangement, the defrost system includes electric heating elements installed within the refrigerated case (near the cooling elements) and periodically energized to heat the cooling surfaces to melt the ice and frost. This arrangement may provide for the removal of ice and frost within a suitable period of time, but requires additional energy and may cause thermal shock or undue heating of objects within the refrigerated case; in addition, thermal cycling may accelerate fatigue and failure of materials within the refrigerated case. According to another known arrangement, the defrost system may be configured to periodically divert or route warm coolant (such as liquid refrigerant or hot gas) otherwise present within the refrigeration cycle of the refrigeration system through the cooling element within the refrigerated case in order to melt the accumulated ice and frost from the cooling surfaces. This arrangement is relatively complex to install and may also result in temperature variations and/or thermal cycling that could have an adverse effect on the refrigerated case or objects within the refrigerated case; this arrangement may also be relatively expensive to install and may create thermal stresses that may tend to increase the possibility of leaks. Such known arrangements for a defrost system typically do not provide for a cost-effective and controllable process for removing ice and frost from the cooling surfaces of the refrigerated case.
Accordingly, it would be advantageous to provide a refrigeration system of a type having at least one refrigeration device (such as a refrigerated case) with a defrost system that can be installed and operated in a relatively cost-efficient and energy-efficient manner. It would also be advantageous to provide for a defrost system that allows for relatively “tight” control of the temperature within the refrigerated case (and of objects within the refrigerated case). It would further be advantageous to provide a defrost system for a refrigeration system that operates relatively quickly to remove ice and frost from cooling surfaces within the refrigerated case but does not require or result in any potentially harmful variation of the temperature of objects within the refrigerated case. It would be further advantageous to provide a defrost system that has a relatively compact modular design that can be used with any of a wide variety of refrigeration systems and refrigerated cases. It would further be advantageous to provide a defrost system that is configured to use a source of heat that is conveniently and readily available within the environment where the refrigeration system is installed.
It would be advantageous to provide a refrigeration system with a defrost system having any one or more of these or other advantageous features.